The budget carrier said new Covid lockdown in Ireland, across the UK and in several other EU countries would hit its new year operations, with January traffic expected to fall to 1.25 million.
From 21 January, Ryanair will "significantly cut" its flight schedules, which it said would result in "few, if any" flights operating to and from Ireland or to the UK from the end of January.
Ryanair said passengers affected by the cancellations would be emailed advising them of their options, including free rebookings and refunds.
